JP6898646B2 - Electrochemical reactor, fuel gas production system and fuel gas production method - Google Patents

Description

The present invention relates to an electrochemical reactor, a fuel gas production system, and a fuel gas production method.

In Japan, the hydrogen of about 15 billion Nm ³ per year have been used in industrial applications of petroleum-related and ammonia manufacturing-related or the like. The hydrogen market is expected to expand further in response to the recent expansion of the use of hydrogen energy.

90% of the hydrogen currently used is produced by steam reforming fossil fuel naphtha. The supply capacity of crude oil, which is the raw material for naphtha, is declining relatively. In addition, the reduction of carbon dioxide in the atmosphere has become a global trend.

Aiming for a low-carbon society, attention is being paid to the use of biogas generated by methane fermentation by methane bacteria from food residues, shochu residue, livestock excrement, sewage sludge, and the like. Biogas is a mixed gas mainly composed of 60% methane and 40% carbon dioxide. The use of thermal energy generated by combustion of biogas and hydrogen gas obtained by reforming biogas suppresses the consumption of fossil fuels such as crude oil and suppresses the emission of carbon dioxide, which is a greenhouse gas.

Hydrogen (H ₂ ) and carbon monoxide (CO) produced by reacting methane (CH ₄ ) and carbon dioxide (CO _{2) can be used as various fuels.} Using the redox reaction at the electrode, a gas containing CH ₄ and CO ₂ as a method for synthesizing a fuel gas containing H ₂ gas and CO gas, nickel (Ni) or the like metal catalyst CH ₄ using the There is dry reforming. Dry reforming is represented by equation (1).
CH ₄ + CO ₂ → 2H ₂ + 2CO (1)

For example, in dry reforming using a Ni catalyst, a _{disproportionation reaction in which CO 2} and carbon (C) are produced from CO occurs at a temperature lower than 600 ° C. as shown in equation (2).
2CO → CO ₂ + C (2)

On the other hand, under high temperature, as shown in Eq. (3), _{the thermal decomposition of CH 4} proceeds, and the precipitated carbon covers the Ni catalyst. Therefore, the catalytic ability decreases with the passage of time. In addition, gas clogging may occur due to the precipitated carbon.
CH ₄ → 2H ₂ + C (3)

Thus, in the dry reforming of biogas, CO disproportionation and CH ₄ carbon deposition by pyrolysis is a large influence on the durability of the electrochemical reactor.

_{In Patent Document 1, a gas containing CH 4} and CO ₂ is dry-formed with an electrochemical reactor using a ruthenium (Ru) -gadolinium (Gd) solid-dissolved ceria (GDC) complex for the cathode and anode. techniques for synthesizing and H ₂ have been proposed. According to Patent Document 1, the electrochemical reactor promoted dry reforming of simulated biogas at 400 to 800 ° C. while suppressing carbon precipitation.

Further, Non-Patent Document 1 discloses an electrochemical reactor including a cathode using a Ni-GDC complex and an anode using a Ru-GDC complex. When supplying a mixed gas of biogas and CO ₂ to the electrochemical reactor, H ₂ -CO mixed fuel outlet gas proportion exceeds 80% was produced continuously for 24 hours.

International Publication No. 2009/157454

Yoshihiro Hirata, 4 outsiders, "Hydrogen formation from real biogas using electrochemical cell with gadolinium-topped ceria electrolyte", Ceria36

In the electrochemical reactor disclosed in Patent Document 1, the outlet gas flow rate increased at a high temperature (700 to 800 ° C.) and a sufficient H ₂ production rate was obtained, but the outlet gas flow rate was compared at 600 ° C. The H ₂ production rate was reduced. Further, the electrochemical reactor disclosed in Non-Patent Document 1, although the H 2 _-CO mixed fuel can be obtained with high efficiency, carbon deposited on the cathode is observed especially 600 to 700 ° C..

Therefore, while further suppressing the carbon deposition, further improvement of the electrochemical reactor so that H ₂ -CO mixed fuel is obtained with a high efficiency is demanded. Further, Ru is used in both the electrochemical reactors disclosed in Patent Document 1 and Non-Patent Document 1. Ru is more expensive than Ni and the like because the amount of Ru present on the earth is much smaller than that of Ni and the like. Therefore, there is room for improvement in terms of cost for manufacturing and maintaining the electrochemical reactor.

The present invention has been made in view of the above circumstances, and provides an electrochemical reactor that can obtain fuel gas with high efficiency while suppressing carbon precipitation, a fuel gas production system, and a fuel gas production method. With the goal.

The electrochemical reactor according to the first aspect of the present invention is
A cathode containing a first metal selected from the group consisting of nickel, ruthenium and cobalt,
An anode containing a second metal, ruthenium or cobalt,
A porous electrolyte membrane that is interposed between the cathode and the anode and contains a metal oxide that allows oxide ions to permeate.
With
Oxidizing agent gas and biogas containing oxygen are supplied toward the cathode.

In this case, the first metal is
Nickel
The second metal is
Cobalt,
It may be that.

In addition, the oxidant gas is
It ’s air,
The ratio of the number of moles of methane contained in the biogas to the total number of moles of oxygen and carbon dioxide contained in the biogas and the air, respectively, is
1: 0.9 to 1.1,
It may be that.

The fuel gas production system according to the second aspect of the present invention is
The electrochemical reactor according to the first aspect of the present invention and
A supply unit that supplies the oxidant gas and the biogas toward the cathode, and
To be equipped.

In this case, the fuel gas production system according to the second aspect of the present invention is
An application unit for applying a pulse voltage between the cathode and the anode is further provided.
It may be that.

Further, the fuel gas production system according to the second aspect of the present invention is described.
Further provided with a holding portion for holding the oxidant gas and the biogas,
The supply unit
The oxidizing agent gas and the biogas held in the holding portion are supplied toward the cathode.
It may be that.

The method for producing a fuel gas according to the third aspect of the present invention is as follows.
An intervening cathode containing a first metal selected from the group consisting of nickel, ruthenium and cobalt, an anode containing a second metal such as ruthenium or cobalt, and oxidation between the cathode and the anode. A method for producing a fuel gas using an electrochemical reactor including a porous electrolyte membrane containing a metal oxide that allows material ions to permeate.
An application step of applying a voltage between the cathode and the anode,
A supply step of supplying oxygen-containing oxidant gas and biogas toward the cathode, and
including.

According to the present invention, fuel gas can be obtained with high efficiency while suppressing carbon precipitation.

It is a figure which shows the structure of the electrochemical reactor which concerns on Embodiment 1. FIG. It is a figure which shows the structure of the fuel gas manufacturing system which concerns on Embodiment 2. It is a figure which shows the schematic cross section of the reactor for experiment in Example 1. FIG. It is a figure which shows the ratio (a) of the outlet gas and the flow rate (b) of the outlet gas in the dry reforming by the cell 1 of the biogas to which CO _{2 was added.} It is a figure which shows the microstructure and element distribution of the cobalt (Co) -GDC cathode after the dry reformation of the biogas by cell 1. (A) shows the microstructure of the Co-GDC cathode. (B) to (g) represent carbon (C), oxygen (O), cobalt (Co), cerium (Ce), gadolinium (Gd) and silicon (Si), respectively. It is a figure which shows the ratio (a) of the outlet gas, the flow rate (b) of the outlet gas, and the current density (c) of a cell 2 in the dry reforming at 600 degreeC by the cell 2 of the biogas added with CO _2. It is a figure which shows the ratio (a) of the outlet gas, the flow rate (b) of the outlet gas, and the current density (c) of a cell 2 in the dry reforming at 800 degreeC by the cell 2 of the biogas added with CO _2. It is a figure which shows the microstructure and element distribution of the Ni-GDC cathode after the dry reformation of biogas at 800 degreeC by cell 2. (A) shows the fine structure of the Ni-GDC cathode. (B) to (f) represent C, O, Ni, Ce and Gd, respectively. It is a figure which shows the ratio (a) of the outlet gas in the dry reforming by the cell 2 of the biogas to which air was added, the flow rate (b) of the outlet gas, and the current density (c) of a cell 2. It is a figure which shows the structure of a cell 3. It is a figure which shows the ratio (a) of the outlet gas in the dry reforming by the cell 3 of the biogas to which CO _{2 was added, the flow rate (b) of the outlet gas, and the current density (c) of cell 3.} It is a figure which shows the ratio (a) of the outlet gas at 700 or 800 degreeC, the flow rate (b) of the outlet gas, and the current density (c) of a cell 3 in the dry reforming by the cell 3 of the biogas to which air was added.

An embodiment of the present invention will be described with reference to the drawings. The present invention is not limited to the following embodiments.

(Embodiment 1)
First, the first embodiment will be described. Electrochemical reactor 100 according to this embodiment, suitable for producing H ₂ -CO mixed fuel as the fuel gas to (also referred to as "modified" in the following) the supplied biogas dry reforming Is. As shown in FIG. 1, the electrochemical reactor 100 includes an electrolyte membrane 1, a cathode 2, and an anode 3.

The electrolyte membrane 1 is porous. The electrolyte membrane 1 contains a metal oxide that allows oxide ions to permeate. The electrolyte membrane 1 is interposed between the cathode 2 and the anode 3. More specifically, the electrolyte membrane 1 is sandwiched and held between the cathode 2 and the anode 3. Examples of the metal oxide include Ce-rare earth element (ytterbium, ytterbium, gadolinium, samarium, neodymium, lanthanum, etc.) oxides, zirconium-ittrium oxides, and lanthanum-gallium oxides. For example, the electrolyte membrane 1 is formed by GDC. The GDC is Ce _0.9 Gd _0.1 O _1.95 or Ce _0.8 Gd _0.2 O _1.9 .

The cathode 2 contains a metal (first metal) selected from the group consisting of Ni, Ru and Co. Preferably, the cathode 2 is a mixture of the metal and a porous electrolyte of an oxide ion conductor. The electrolyte is, for example, GDC.

The anode 3 contains a metal (second metal) that is Ru or Co. Like the cathode 2, the anode 3 is preferably a mixture of the metal and the porous electrolyte of the oxide ion conductor. Preferably, the metal contained in the cathode 2 is Ni and the metal contained in the anode 3 is Co.

Preferably, the electrochemical reactor 100 is formed in a columnar shape as shown in FIG. Although it depends on the volume of the biogas to be processed and the like, the diameter of the circle of the cross section obtained by cutting the electrochemical reactor 100 perpendicularly to the height direction of the cylinder is, for example, 5 mm to 15 mm, 8 mm to 12 mm, preferably 10 mm. .. When the diameter of the circle is 10 mm, the axial thickness of the cathode 2 and the anode 3 is 2 to 10 mm, preferably 3 to 6 mm, and the axial thickness of the electrolyte membrane 1 is 10 to 200 μm, preferably 10 to 200 μm. It is 50 to 100 μm.

Next, a method for manufacturing the electrochemical reactor 100 will be described. Hereinafter, a case where the electrolyte membrane 1, the cathode 2 and the anode 3 are manufactured by using the GDC will be described. The GDC powder can be produced, for example, by the oxalate coprecipitation method. When the GDC powder is produced by the oxalate coprecipitation method, first, the Ce (NO ₃ ) ₃ aqueous solution and the Gd (NO ₃ ) ₃ aqueous solution are mixed at a molar ratio of Ce and Gd of 9 to 3: 1. Then, this mixed solution is added to the oxalic acid aqueous solution and coprecipitated. GDC powder is obtained by calcining the obtained oxalate at 500 to 800 ° C., preferably 600 ° C. in air. Next, by further pulverizing the GDC powder, a fine GDC powder can be obtained.

To form the electrolyte membrane 1 with the GDC powder, the GDC powder is dispersed in, for example, a mixed organic solvent of isopropanol and toluene. Subsequently, a binder such as polyvinyl butyral and a plasticizer such as polyethylene glycol are added to the obtained suspension. The amounts of binder and plasticizer are adjusted as appropriate. The amount of binder is 2-8%, 4-6%, preferably 5% with respect to the mass of the GDC powder. The amount of the plasticizer is 5 to 15%, 8 to 12%, preferably 9% with respect to the mass of the GDC powder. Then, the suspension may be formed into an electrolyte with a doctor blade device or the like.

Next, a method for manufacturing the cathode 2 and the anode 3, that is, the electrodes will be described. First, the aqueous solution containing any of the above metals and the GDC powder are mixed. Then, it is freeze-dried and the obtained powder is calcined at 600 to 800 ° C. for about 1 hour to obtain a mixed powder of a metal oxide and GDC (metal oxide-GDC). The metal oxide-GDC is hydrogen-reduced into a metal-GDC mixed powder. The pH may be adjusted as appropriate before freeze-drying. In the method for producing an electrode, the metal and GDC are mixed so as to have a volume ratio of 4: 6 to 1: 9, preferably 3: 7 to 2: 8.

More specifically, when the electrode is manufactured from a mixture of Co and GDC (Co-GDC), _{two aqueous Co (NO 3} ) solutions and GDC powder are used so that the volume ratio is Co: GDC = 3: 7. To mix. Then, it is freeze-dried and calcined in air at 600 ° C. for 1 hour _{to obtain a Co 3} O _4- GDC mixed powder.

When the electrode is manufactured from a mixture of Ni and GDC (Ni-GDC), the Ni (NO ₃ ) ₂ aqueous solution and the GDC powder are mixed so that the volume ratio is Ni: GDC = 3: 7. Then, it is freeze-dried and calcined in air at 800 ° C. for 1 hour to obtain a NiO-GDC mixed powder.

When the electrode is manufactured from a mixture of Ru and GDC (Ru-GDC), the RuCl ₃ aqueous solution and the GDC powder are mixed so that the volume ratio is Ru: GDC = 3: 7. The pH is adjusted to 10 with aqueous ammonia, the mixture is stirred for 24 hours, and then freeze-dried. The obtained powder 800 ° C., 1 hour, obtaining a _RuO 2 -GDC mixed powder was calcined in air.

As shown in FIG. 1, the metal oxide-GDC used for the cathode 2, the electrolyte film 1, and the metal oxide-GDC used for the anode 3 so that the electrolyte film 1 is sandwiched between the cathode 2 and the anode 3. And are laminated in a tablet molding machine, and uniaxially pressurized at 50 to 100 MPa, 60 to 90 MPa, preferably 80 MPa. Subsequently, the laminate is isotropically pressurized at 150 to 300 MPa, 180 to 220 MPa, preferably 200 MPa, and then cosintering is performed at 1200 ° C. for 2 hours in air.

Preferably, the relative densities of the co-sintered cathode 2 and anode 3 are 70-90%, 75-85% or 80-85%. The open porosity of the cathode 2 and the anode 3 is 12 to 22%, 14 to 20% or 15 to 19%. The porosity of the cathode 2 and the anode 3 is 0 to 3% or 0 to 2%.

Furthermore, _{H 2} atmosphere, by performing the reduction treatment at about 12 to 24 hours at 800 ° C., to reduce the metal contained in the cathode 2 and anode 3. By this reduction treatment, for example, NiO, Co ₃ O ₄ and RuO ₂ contained in the cathode 2 and the anode 3 are reduced to Ni, Co and Ru, respectively.

Subsequently, the operation of the electrochemical reactor 100 will be described. The electrochemical reactor 100 is inserted into a tube 4 made of, for example, alumina or the like, and its temperature is maintained at 500 to 1000 ° C., preferably 600 to 900 ° C. for use. In the electrochemical reactor 100, an oxidant gas and a biogas containing _{O 2 are supplied toward the cathode 2.}

The oxidant gas is O ₂ gas, preferably air. The oxidant gas and the biogas may be individually supplied to the cathode 2 as long as they are supplied to the cathode 2 at the same time. Preferably, a raw material gas in which an oxidant gas and a biogas are mixed is supplied to the cathode 2.

In the electrochemical reactor 100, a voltage of about 1 to 5 V is applied between the cathode 2 and the anode 3 by the application unit 5. Here, when the raw material gas is supplied to the cathode 2, the reduction reaction represented by the equation (4) occurs at the cathode 2. That is, the cathode 2 produces from CO ₂ CO and oxide ions ^{(O 2-).
_{CO 2 + 2e - → CO +}} O 2- (4)

The electrolyte membrane 1 allows CH ₄ supplied to the cathode 2 and O ^2- generated by the cathode 2 to permeate. _{CH 4} and O ^{2- that} have passed through the electrolyte membrane 1 reach the anode 3. Then, when CH ₄ and O ^2- reach the anode 3, the oxidation reaction represented by the equation (5) occurs at the anode 3. That is, CO and H ₂ are produced _{from CH 4} and O ^2-.
CH ₄ + O ^2- → CO + 2H ₂ + 2e ⁻ (5)

Therefore, the reaction formula of all the reactions in the electrochemical reactor 100 is represented by the formula (6).
CH ₄ + CO ₂ → 2H ₂ + 2CO (6)

The electrochemical reactor 100 can efficiently produce fuel gas by dry reforming by controlling the temperature under the applied voltage. On the other hand, as shown in the following Examples 2 and 4, the temperature rise under the applied voltage is, CH ₄ pyrolysis not dry reforming only (above (2)) and carbon monoxide disproportionation reaction (the It also promotes carbon precipitation according to equation (3) (competitive parallel reaction).

On the other hand, in the electrochemical reactor 100, as described above, the oxidant gas containing _{O 2 is supplied to the cathode 2 together with the biogas.} The supplied O ₂ functions as an oxidizing agent and oxidizes the precipitated carbon as shown in the formula (7). As a result, carbon precipitation is suppressed.
2C + O ₂ → 2CO (7)

The concentration (vol%) of each component in biogas is usually about 60% for _{CH 4 and about 40% for CO 2,} but 0.1 to 0.7% or less than 1% O ₂ . May include. To the cathode 2, O ₂ other than O ₂ contained in the biogas itself need be supplied with biogas. The ratio of the supply amounts of the oxidant gas and the biogas is preferably set based on the stoichiometric ratio. When air is used as the oxidant gas, the ratio of the number of moles of _{CH 4} contained in the biogas to the total number of moles of _{O 2 and CO 2} contained in each of the biogas and air is 1: 0. It is .8 to 1.4, 1: 0.9 to 1.2, preferably 1: 0.9 to 1.1. _{Further, for example, the molar ratio of CH 4} , CO ₂ and O ₂ in the above raw material gas is 3: 1.5 to 2.4: 0.5 to 1.6, 3: 1.6 to 2.2 :. It may be adjusted to 0.8 to 1.5 or 3: 1.8 to 2.0: 1.0 to 1.4, preferably 3: 1.9: 1.3.

As described in detail above, in the electrochemical reactor 100, the oxidant gas containing _{O 2 is supplied to the cathode 2 together with the biogas.} By doing so, carbon is oxidized, so that the precipitation of carbon can be suppressed as shown in Examples 3 and 4. The electrochemical reactor 100 has high durability for long-term operation because the high activity of the metal catalyst can be maintained by removing the precipitated carbon. It is also considered that the supplied O ₂ is also used for reforming biogas. Therefore, the electrochemical reactor 100 can obtain fuel gas with high efficiency as shown in Examples 3 and 4 below.

Further, in the present embodiment, the metal contained in the cathode 2 may be Ni and the metal contained in the anode 3 may be Co. In this way, the electrochemical reactor 100 exhibits excellent reforming efficiency, as shown in Example 5 below. Furthermore, Co is cheaper than Ru and exhibits catalytic activity equal to or higher than that of Ru, as shown in Example 5 below. Therefore, the use of Co is advantageous in terms of cost in the manufacture and maintenance of the electrochemical reactor 100.

The amount of metal contained in the cathode 2 and the anode 3 is not uniform and may be inclined. For example, the metal content of the cathode 2 in the laminate may be gradually increased as the distance from the anode 3 increases. Similarly, the metal content of the anode 3 in the laminate may be gradually increased as the distance from the cathode 2 increases. More specifically, the anode 3, Co: GDC = 3: 7 of _Co 3 _O 4 the first layer was prepared from -GDC mixed powder and _{Co: GDC = 2: 8 Co} 3 O 4 -GDC mixing A second layer made from powder may be provided. In this case, in the laminated body, the second layer is arranged between the electrolyte membrane 1 and the first layer. The same applies to the cathode 2. By doing so, it is possible to prevent the cathode 2 or anode 3 from peeling off from the electrolyte membrane 1 during sintering.

(Embodiment 2)
Next, the second embodiment will be described with reference to FIG. The fuel gas production system 200 according to the second embodiment includes the electrochemical reactor 100 according to the first embodiment, an application unit 5, a holding unit 6, a supply unit 7, and a temperature control unit 8. Be prepared.

The configuration of the electrochemical reactor 100 is the configuration described in the first embodiment. The application unit 5 applies a voltage of about 1 to 5 V between the cathode 2 and the anode 3. The application unit 5 is composed of, for example, a potentiostat, and is connected to the electrochemical reactor 100 by adhering a platinum mesh current collector to which a platinum lead wire is welded to the surfaces of each of the cathode 2 and the anode 3. The voltage applied by the application unit 5 may be a DC voltage or a pulse voltage. Preferably, the application unit 5 applies a pulse voltage between the cathode 2 and the anode 3.

The holding unit 6 holds the above-mentioned oxidizing agent gas and biogas. The holding unit 6 may hold the raw material gas in which the above-mentioned oxidant gas and biogas are mixed, or may hold the oxidant gas and the biogas individually. The holding unit 6 holds the oxidant gas and the biogas in a container such as a cylinder and a tank.

The supply unit 7 supplies the above-mentioned oxidizing agent gas and biogas toward the cathode 2. More specifically, the supply unit 7 supplies the oxidant gas and the biogas held in the holding unit 6 toward the cathode 2. For example, the holding unit 6 is connected so as to be able to supply gas to the electrochemical reactor 100, and the oxidant gas and biogas held in the holding unit 6 are supplied to the cathode 2 via the supply unit 7.

The supply unit 7 controls the supply amounts of the oxidant gas and the biogas. For example, when the holding unit 6 separately holds air and biogas as an oxidant gas, the supply unit 7 supplies air at 40 to 60 ml / min, whereas biogas is supplied at 30 to 50 ml / min. Supply with. When the holding unit 6 holds the raw material gas, the supply unit 7 supplies air at 50 to 150 ml / min. In the supply unit 7, the ratio of the number of moles of _{CH 4} contained in the biogas to the total number of moles of _{O 2 and CO 2} contained in each of the biogas and biogas is as described above. It may be supplied in a ratio, or the above-mentioned raw material gas may be supplied.

The temperature control unit 8 controls the temperature of the electrochemical reactor 100 to 500 to 1000 ° C, preferably 600 to 900 ° C. The temperature control unit 8 includes an unlimited heating device, and controls the temperature of the electrochemical reactor 100 via the heating device. The temperature control unit 8 includes, for example, an electric furnace as a heating device, and controls the temperature of the electrochemical reactor 100 installed in the electric furnace. The temperature control unit 8 may flexibly control the temperature of the electrochemical reactor 100 by monitoring the temperature of the electrochemical reactor 100 with a thermoelectric pair or the like.

As described in detail above, since the fuel gas production system 200 includes the supply unit 7, the _{oxidant gas containing O 2} can be reliably supplied to the cathode 2 together with the biogas. Further, since the fuel gas production system 200 includes the application unit 5, the reduction reaction at the cathode 2 _{can be promoted and CO 2} can be efficiently decomposed.

Further, the fuel gas production system 200 can supply the oxidant gas containing _{O 2} to the electrochemical reactor 100 at a mixing ratio optimized by providing the holding unit 6. By doing so, it is possible to efficiently produce fuel gas while suppressing carbon precipitation as much as possible, and it is possible to bring about long-term durability.

Further, in the fuel gas manufacturing system 200, the application unit 5 may apply a pulse voltage between the cathode 2 and the anode 3. By using the pulse voltage, the power consumption can be suppressed as compared with the case of using the DC voltage.

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the examples.

(Example 1: Preparation of cell 1 and cell 2)
Cell 1 and cell 2 were produced as two types of electrochemical reactors as follows. Cell 1 comprises a GDC porous electrolyte membrane, cathode and anode. The GDC is Ce _0.9 Gd _0.1 O _1.95 . The cathode of cell 1 is Co (30 vol%) -GDC (70 vol%), and the anode of cell 1 is Co (30 vol%) -GDC (70 vol%).

Cell 2 comprises the same GDC porous electrolyte membrane, cathode and anode as cell 1. The cathode of cell 2 is Ni (30 vol%) -GDC (70 vol%), and the anode of cell 2 is Co (30 vol%) -GDC (70 vol%).

The above GDC was prepared by the oxalate coprecipitation method as follows. A 0.2 M Ce (NO ₃ ) ₃ aqueous solution and a 0.2 M Gd (NO ₃ ) ₃ aqueous solution were mixed so that the molar ratio was Ce: Gd = 9: 1. The mixed solution was added dropwise to a 0.4 M aqueous oxalic acid solution and coprecipitated as a _{solid oxalate solution (Ce 0.9} Gd _0.1 ) ₂ (C ₂ O ₄ ) _3. The obtained oxalate was calcined in air at 600 ° C. for 1 hour to obtain a GDC powder. The GDC powder was pulverized with an alumina ball having a diameter of 3 mm to obtain fine GDC particles. GDC particles were dispersed in an organic solvent containing 67 vol% isopropanol and 33 vol% toluene in a solid amount of 25 vol%. Polyvinyl butyral as a binder and polyethylene glycol as a plasticizer were added to the suspension in an amount of 5% and 9%, respectively, based on the mass of the GDC powder. The suspension was prepared as an electrolyte membrane having a thickness of 100 μm by a doctor blade device having an opening of 170 μm in the front blade.

In the preparation of the electrodes, in the case of Co-GDC, a 1.0 M Co (NO ₃ ) ₂ aqueous solution was mixed with the GDC powder so that the volume ratio was Co: GDC = 3: 7. Then, it was freeze-dried and calcined in air at 600 ° C. for 1 hour _{to obtain a Co 3} O _4- GDC mixed powder. On the other hand, in the case of Ni-GDC, a 1.4M Ni (NO ₃ ) ₂ aqueous solution was mixed with the GDC powder so that the volume ratio was Ni: GDC = 3: 7. Then, it was freeze-dried and calcined in air at 800 ° C. for 1 hour to obtain a NiO-GDC mixed powder.

The electrolyte membrane, cathode powder (Co ₃ O ₄ -GDC mixed powder or NiO-GDC mixed powder), and anode powder (Co ₃ O ₄ -GDC mixed powder) are laminated in a tablet molder having a diameter of 10 mm. , 80 MPa was uniaxially pressurized. Then, the laminate was isotropically pressurized at 200 MPa, and then co-sintered at 1200 ° C. for 2 hours in air. The bulk density and apparent density of the co-sintered electrodes were measured by the Archimedes method using redistilled water. The relative density, open porosity and closed porosity of the Co ₃ O _4- GDC cathode were 81.7%, 18.3% and 0%, respectively. The relative density, open porosity and closed porosity of the NiO-GDC anode were 83.2%, 15.3% and 1.6%, respectively.

As shown in FIG. 3, a platinum mesh current collector to which a platinum lead wire was welded was adhered to each surface of a cathode and an anode using a platinum paste, and baked at 870 ° C. Cell 1 was installed in a porcelain tube. The gap between the cell 1 and the magnetic tube was sealed by heating the glass ring in air at 870 ° C. Then, the reactor for the experiment was manufactured by sealing the porcelain tube and the silica-alumina tube with a glass ring. An experimental reactor was similarly prepared for cell 2.

Ni O _{and Co 3 O 4} in the electrode were reduced at 800 ° C. for 8 hours _{in an H 2} atmosphere to which 3 vol% of water vapor was added to produce metallic Ni and metallic Co. After purging with H ₂ gas with argon gas, it was dry reforming of biogas using the cell 1 and cell 2 obtained. The temperatures of cell 1 and cell 2 were controlled by an electric furnace.

(Example 2: Dry reformation of biogas by _{CO 2} using cells 1 and 2)

Shochu lees biogas (manufactured by Seisatsu Clean Sunset Business Cooperative) was used as the biogas. The chemical composition of the biogas was 60.0 vol% CH ₄ , 37.5 vol% CO ₂ , 2.5 vol% N ₂ , 0.1 vol% O ₂ , 2.1 ppm hydrogen sulfide (H ₂ S). High-purity CO ₂ (purity> 99.99%) was mixed with biogas to adjust _{the dry reforming stoichiometric ratio to CH 4} / CO _{2 = 1/1.} 40 ml / min biogas and 10 ml / min CO ₂ were mixed and supplied to cell 1 and cell 2, respectively.

Using a potentiostat / galvanostat (HAL-3001, manufactured by Hokuto Denko Co., Ltd.), a voltage of 0 to 2 V was applied to each of cell 1 and cell 2, and the current densities of cell 1 and cell 2 were measured. The outlet gas composition was measured by using a gas chromatograph (GC7100T, manufactured by J-Science Lab) having an activated carbon column and a thermal conductivity detector, using argon as the carrier gas. The temperatures of the activated carbon column and the thermal conductivity detector were 70 ° C and 100 ° C, respectively. The current supplied to the thermal conductivity detector was 60 mA. The flow rate of the outlet gas was measured with a soap film flow meter (3001-1102, manufactured by GL Sciences Co., Ltd.). After the dry reforming experiment, the constituent phases of cells 1 and 2 were identified using an X-ray diffractometer (RINT2200 PCH / KG, manufactured by Rigaku). The precipitation of carbon in the reactor was analyzed with an electron probe microanalyzer (JXA-8230, manufactured by JEOL Ltd.).

(result)
FIG. 4 shows the ratio (a) of the outlet gas and the flow rate (b) of the outlet gas in the dry reforming of the biogas by _{CO 2 using the cell 1.} The temperature of the reactor was 200 to 800 ° C., and the applied voltage was 0 V or 1 V. Generation of H ₂ gas and CO gas were measured at 600 ° C. or higher. H ₂ exit gas rate of gas and CO gas are from 2.8 to 5.2% and from 6.2 to 9.0%, respectively at 600 ° C., respectively 800 ° C. 20.1-27.3 percent and 27. It increased to 4-30.6%. The flow rate of each gas was almost constant at each temperature. ^{A current of 0.197 A / cm 2} flowed when a voltage of 1 V was applied. However, the applied voltage did not affect the ratio and flow rate of _{H 2 gas and CO gas.} In the gas chromatograph device used, it was difficult to separate _{O 2} and N _2.

The following reactions can be considered as the generation mechanism _{of H 2} and CO when the applied voltage is 1 V.
Cathode Co + CO ₂ → CoO + CO (8)
^{CoO + 2e - → Co + O} 2- (9)
Anode Co + O ^2- → CoO + 2e ⁻ (10)
CoO + CH ₄ → Co + CO + 2H ₂ (11)
Total reaction CH ₄ + CO ₂ → 2CO + 2H ₂ (12)

The above reaction process shows _{the interaction between CO 2} and Co catalyst at the cathode and the interaction between CH ₄ and Co catalyst at the anode. _However, H 2 -CO fuel mixture produced any 0V. This result shows that the reaction processes of Eqs. (9) and (10) are omitted. That is, it is considered that the dry reforming reaction represented by the formula (12), which is a combination of the formulas (8) and (11), proceeds on the Co catalyst in the cathode or the anode.

According to FIG. 4, the applied voltage at 600-800 ° C. does not affect the outlet gas ratio and flow rate. This result indicates that the dry reforming of the biogas on the Co catalyst at 600 to 800 ° C. proceeded mainly thermodynamically.

FIG. 5 shows the microstructure (a) and elemental distribution ((b) to (g)) of the Co-GDC cathode after dry reforming of biogas at 200 to 800 ° C. for 8 hours in cell 1. The distribution of the silicon element (Si) is derived from the glass that seals the gap between the cell 1 and the cell 2 and the magnetic tube. As shown in FIG. 5 (b), a small amount of carbon precipitation was observed. The supplied CO ₂ is reduced to produce CO gas and an O atom (CoO of equation (8)). Carbon is not produced from the _{supplied CO 2.} The observed carbon was generated from _{CH 4} supplied on the Co catalyst _{(CH 4} → C + 2H ₂ ). The distribution of carbon overlaps with the distribution of metal Co and GDC electrolyte, and the formation of carbon and water vapor by the thermal decomposition _{of CH 4 on metal Co (CH 4} → C + 2H ₂ ) and _{the interaction between CH 4 and GDC lattice oxygen.} Suggest. This competitive reaction proceeds with the dry reforming of the biogas represented by Eq. (12).

The microstructures of the Co-GDC anode and GDC electrolyte were also observed. The carbon content detected in the anode or electrolyte was very low compared to the cathode. This result indicates that the metal Co in the cathode interacts with both _{CO 2} and CH _{4 supplied.}

_{FIG. 6 shows the ratio (a) of the outlet gas for dry reforming of biogas by CO 2} at 600 ° C. using the cell 2, the flow rate (b) of the outlet gas, and the current density (c) of the cell 2. The applied voltage was 0.5V. H ₂ gas and CO gas were continuously produced 6 hours. The proportion of the outlet gas of the H ₂ gas and CO gas were respectively 7.7 to 31.5% and from 9.3 to 17.8%. Volume ratio of H ₂ gas / CO gas approached 1 to 2 hours after the modification start. This indicates that the stoichiometric reaction _{between CH 4} and CO _{2 proceeded.}

Total gas flow rate was almost constant for 6 hours at 60 ml / min, but the flow rate of H ₂ gas and CO gas was gradually decreased with the modification time. The rapid decrease in gas flow rate and current density caused by reforming for 6 hours or more is considered to be related to the precipitation of carbon in cells 1 and 2.

_{FIG. 7 shows the ratio (a) of the outlet gas for dry reforming of biogas by CO 2} at 800 ° C. using the cell 2, the flow rate (b) of the outlet gas, and the current density (c) of the cell 2. Increasing the temperature to 800 ° C. exit gas rate of _{H 2} gas and CO gas increased to respectively 37.6 to 46.7% and from 38.4 to 42.6%. H ₂ gas and CO gas were generated 28 hours stably. The volume ratio of H ₂ / CO was almost 1, and the stoichiometric dry reforming reaction of _{CH 4} and CO _{2 proceeded.} The flow rate of the outlet gas shown in FIG. 7B gradually decreased from 61.4 ml / min after the start of reforming to 5.9 ml / min 28 hours later. The current density shown in FIG. 7 (c) ^{rapidly decreased from 1.74 A / cm 2 at the} start of reforming to 0.10 A / cm ² after 5 hours. After that, it was almost constant at 0.05 to 0.1 A / cm ^2. Flow rate and current density of the outlet gas of the H ₂ gas and CO gas was not recovered by an increase in applied voltage.

FIG. 8 shows the microstructure and elemental distribution of the Ni—GDC cathode of cell 2 after biogas dry reforming at 800 ° C. for 28 hours. Carbon precipitation was observed on and inside the cathode. This carbon precipitation caused a gradual decrease in the gas flow rate shown in FIG. 7 (b).

(Example 3: Examination of the effect of air addition in cell 2 on dry reforming)
Modification of biogas with O ₂ in the cell 2 in air was also investigated. 40 ml / min of biogas and 50 ml / min of air were mixed and supplied to cell 2. The molar ratio of gas is CH ₄ / CO ₂ / O ₂ = 3 / 1.875 / 1.314. Other conditions are the same as in Example 2 above.

(result)
FIG. 9 shows the ratio (a) of the outlet gas in the dry reforming of the biogas when air is added to the biogas, the flow rate (b) of the outlet gas, and the current density (c) of the cell 2. The temperature of the reactor was 600 ° C or 800 ° C. The outlet gas ratio and flow rate were stable for 8 hours. In _{the dry reforming of biogas with CO 2, a mixed fuel having a volume ratio of H 2} / CO of 1/1 at 800 ° C. and 0.3 to 1.0 V was produced at an outlet gas ratio of more than 80%. The chemical composition when biogas (40 ml / min) and air (50 ml / min) are mixed is 3CH ₄ + 1.875CO ₂ + 1.314O ₂ + 5.005N ₂ . CH ₄ reacts with _{CO 2} contained in biogas _{and O 2} gas in mixed air. The composition of the reformed gas at 800 ° C is 3.1 to 6.3% CH ₄ , 2.7 to 5.0% CO ₂ , 36.8 to 41.1% H ₂ , 28.8 to 31.6. % CO, it was 21.6~23.1% _{N 2} -O 2.

The reforming reactions considered from the chemical composition of the supplied gas are shown in equations (13) to (15).
3CH ₄ + 1.875CO ₂ +1.314O ₂ +5.005N ₂
= 4.875CO + 6H ₂ + 0.7515O ₂ + 5.005N ₂ (13)
= 3.372CO + 1.503CO ₂ + 6H ₂ + 5.005N ₂ (14)
= 4.875CO + 4.497H ₂ +5.005N ₂ +1.503H ₂ O (15)

Table 1 compares the ratio of the outlet gas when the dry reforming of the biogas with air was performed at 800 ° C. for 2 hours with the above calculated value. The measured CO ₂ ratio, H ₂ / CO molar ratio, and (N ₂ + O ₂ ) / CO molar ratio were in the best agreement with the calculated values in Eq. (13). From this analysis result, the following two things can be said. (1) CH ₄ in biogas is modified by both _{CO 2 contained in biogas and O 2} derived from air. (2) The produced CO and H ₂ are not oxidized by the residual O _2. The measurement results of FIG. 9 and the analysis results of the outlet gas ratio in Table 1 show that air can be used for reforming biogas.

Even when the temperature was lowered to 600 ° C., the outlet gas ratio and the flow rate of the mixed fuel showed relatively high values. As shown in FIG. 9 (c), the current density of this reactor showed a good response to the applied voltage. This is different from the measurement result shown in FIG. 7 (c). This suggests that carbon precipitation in the reactor of FIG. 9 was suppressed. Oxidation of precipitated carbon by the supplied air (2C + O ₂ → 2CO) is one of the possible factors for suppressing carbon precipitation.

(Example 4: Preparation of cell 3 and dry reforming of biogas using cell 3)
Cell 3 was made with a GDC porous electrolyte, a Ni (20 or 30 vol%) -GDC (80 or 70 vol%) cathode, and a Ru (20 or 30 vol%) -GDC (80 or 70 vol%) anode. FIG. 10 shows the structure of cell 3. Thickness of Ni (20 vol%) -GDC (80 vol%), Ni (30 vol%) -GDC (70 vol%), Ru (20 vol%) -GDC (80 vol%) and Ru (30 vol%) -GDC (70 vol%) Each was set to 2 mm. The thickness of the electrolyte membrane was 80 μm. By inclining the metal content of the electrode material to 20 to 30 vol%, peeling between the electrode and the electrolyte during sintering was prevented. The preparation of the electrolyte powder, the electrolyte membrane and the NiO-GDC cathode powder was the same as in Example 1 above. In the preparation of RuO ₂ -GDC anode powder, a RuCl ₃ solution and GDC powder Ru: volume ratio of GDC is 2: 8 or 3: 7 was mixed so. The pH was adjusted to 10 with aqueous ammonia, the mixture was stirred for 24 hours, and then freeze-dried. The obtained powder 800 ° C., 1 hour, and calcined in air _to give RuO 2 -GDC powder. The electrolyte membrane, the cathode powder, and the anode powder were laminated in the tablet molding machine having a diameter of 10 mm in the order shown in FIG. 10, and uniaxially pressurized at 100 MPa. Then, the laminate was isotropically pressurized at 298 MPa, and then co-sintered at 1200 ° C. in air for 2 hours.

A platinum mesh current collector was adhered to each surface of the cathode and the anode in the same manner as in Example 1, and the cell 3 was placed in a porcelain tube. The gap between the cell 3 and the magnetic tube was sealed by heating the glass ring in air at 870 ° C. NiO and RuO ₂ in the electrode are in _{H 2} atmosphere, 800 ° C., which is reduced to metallic Ni and metallic Ru in 12 hours. After purging with H ₂ gas with argon gas, were dry reforming of biogas at 700 or 800 ° C.. The chemical composition of biogas A used as the biogas is the same as that of the biogas used in Example 2, and the chemical composition of biogas B is 55.6 vol% CH ₄ , 37.7 vol% CO ₂ , 5.7 vol% N. _{It was 2} , 0.7 vol% O ₂ , 1.1 ppm H ₂ S. Biogas A or B was fed into cell 3 at 40 ml / min.

_{CO 2} or air was supplied as a deficient oxidant for CH _{4 rich biogas.} In the _{addition of CO 2 , CO 2} was supplied at 10 ml / min so that the stoichiometric ratio of dry reforming was CH ₄ / CO ₂ = 1/1 (CH ₄ + CO ₂ → 2H _{2 + 2CO).} Air addition was performed at a supply rate of 0 to 50 ml / min. Table 2 shows the relationship between the dry reforming reaction of biogas and the amount of air added. When the amount of air added is 10 ml / min or less, the oxidant becomes insufficient, and when 20 ml / min or more, the oxidant becomes excessive. The voltage was applied at 0.5 V with a direct current or a rectangular pulse of 0.1 to 100 Hz. The pulse time was controlled so that the ratio of the voltage applied time to the unapplied time was 1: 1. The outlet gas composition and the outlet gas flow rate were measured in the same manner as in Example 2. The current density of cell 3 was measured with a high-speed data acquisition unit (SL-1000, manufactured by Yokogawa Meter & Instrument Co., Ltd.).

(result)
FIG. 11 shows the ratio of the outlet gas at 800 ° C. (a), the flow rate of the outlet gas (b), and the current density (c) of the cell 3 in the dry reforming of the biogas A to which _{CO 2 is added.} Just after reforming start to produce the mixed fuel of 29.6% _{H 2} gas -32.9% CO gas. The ratio of H ₂ gas and CO gas in the outlet gas decreased with time to 8.9% H ₂ gas-17.4% CO gas after 12 hours. The increase in pulse frequency promoted this performance degradation. In particular, the decrease in the outlet gas flow rate was remarkable at 10 Hz and above. A sharp drop in current occurred at 100 Hz. A DC voltage was applied again after the reforming rate decreased, but the reforming rate did not recover. After the experiment, a large amount of carbon precipitation was observed on the cathode. This caused a decrease in the flow rate of the produced gas.

FIG. 12 shows the ratio of the outlet gas at 700 or 800 ° C. (a), the flow rate of the outlet gas (b), and the current density (c) of the cell 3 in the dry reforming of the biogas B to which air was added. When air was supplied at 50ml / min, it occurs stable generation of H ₂ gas and CO gas was not observed decrease in the rate of reforming for 24 hours. The proportion of H _{2 in} the outlet gas was 36.9-40.9% at 800 ° C. and 34.5-36.0% at 700 ° C. The proportion of CO in the outlet gas was 16.7 to 20.5% at 800 ° C. and 17.0 to 18.8% at 700 ° C. The production of the mixed fuel rich in H _{2 corresponds to the reaction in Table 2 (3CH 4} + 2.034CO ₂ + 1.416O ₂ → 6H ₂ + 5.034CO + 0.933O ₂ ). In addition, unreacted O ₂ is used to remove carbon generated during modification (2C + O ₂ → 2CO). On the other hand, when O ₂ was not supplied at _{800 ° C., the rate of H 2} and CO production also decreased. This also corresponds well with the reaction formulas in Table 2. The current density at 800 ° C. reached the limit value of the measuring device. The current density decreased by about 3 orders of magnitude when the temperature decreased to 700 ° C. On the other hand, the H ₂ production rate hardly decreases, and the modification is promoted with a small current density. Analysis of the reactor after modification using an electron probe microanalyzer showed that almost no carbon precipitation occurred.

The above results suggest that NiO with low conductivity is produced by being oxidized by the air to which a part of Ni and Ru is added at 700 ° C. RuO ₂ is an oxide, but its electron conductivity is as high as Ru. In addition, ^{the diffusion rate of the generated O 2-} ion also decreases at 700 ° C. At 800 ° C., NiO is quickly reduced to Ni by the supplied electrons (NiO + 2e ⁻ → Ni + O ^2- ), and the diffusion rate of the ^{generated O 2- ions is also high.} Therefore, it is considered that the current density showed a high value.

In this example, when CO ₂ was added, the reforming rate gradually decreased at 800 ° C. The decrease in the reform rate was promoted by the increase in the pulse frequency. This is because carbon is precipitated in parallel during gas reforming. The addition of air suppressed this decrease in the reforming rate, and stable production of the mixed fuel was observed at 700 or 800 ° C. for 24 hours. This is because it is converted in O ₂ where the produced carbon was supplied to the CO gas.

(Example 5: Comparison of modification efficiency of an electrochemical reactor having a porous GDC electrolyte)
In dry reforming of biogas using _{CO 2} or O _{2 , a high conversion rate from CH 4} to H _2- CO mixed fuel and high durability for long-term operation are required for the electrochemical reactor. The interaction between the metal catalyst in the electrode and CH _{4 decomposes CH 4} to produce solid carbon. This greatly affects the durability of the reactor. Weak catalytic activity for the degradation of CH ₄ is important, especially at the cathode. On the other hand, the reforming reaction proceeds thermodynamically on the metal catalyst of the cathode at 800 ° C. and electrochemically on the metal catalyst of both electrodes at 600 ° C. The modification efficiency at low temperature depends on the interaction between _{CO 2} at the cathode and the metal catalyst and the interaction between CH _{4 at the anode and the metal catalyst.}

A cell (Comparative Example 1) having a GDC electrolyte as in cell 1 above, having a cathode of Ni (30 vol%) -GDC (70 vol%) and an anode of Ni (30 vol%) -GDC (70 vol%), a cathode. Is Ru (30 vol%) -GDC (70 vol%), the anode is Ru (30 vol%) -GDC (70 vol%) (Comparative Example 2), and the cathode is Ni (30 vol%) -GDC (70 vol%). Then, a cell (Comparative Example 3) in which the anode was Ru (30 vol%) -GDC (70 vol%) was prepared in the same manner as in Example 1 above. See Example 4 for the preparation of RuO _{2-GDC powder.} In addition to cell 1 and cell 2, it was dry reforming of _50% CH 4 -50% CO ₂ gas mixture in Comparative Examples 1 to 3 at respective temperatures.

Table 3 _shows a comparison between the cells of the production rate of 50% CH 4 -50% CO ₂ dry reforming of the mixed gas _{H 2 (f (H 2)} ) and CO production rate (f (CO)) .. The production rates were compared within 2 hours from the start of reforming, which is less affected by the deterioration of the reactor due to carbon precipitation. The flow rate of the outlet gas _{depends on the supply rate of the CH 4-} CO ₂ mixed gas, the pore size distribution of the electrodes, and the reforming efficiency of the reactor. In order to evaluate the reforming efficiency, the H ₂ and CO production rates were standardized at the outlet gas flow rate of 50 ml / min.

The anode of Ni (Comparative Example 1) promoted rather CH ₄ pyrolysis than dry reforming in applied voltage under 1V. _{The rate of formation of H 2} at 600 ° C. increased in the order of Comparative Example 3 <Cell 1 <Comparative Example 2 <Cell 2. _{The rate of formation of H 2} at 800 ° C. increased in the order of cell 1 <comparative example 2 <comparative example 3≈cell 2. At 800 ° C, the difference in production rate between reactors was smaller than at 600 ° C. As a result, cell 2 having a Ni catalyst at the cathode and a Co catalyst at the anode showed the highest modification efficiency.

For details of Comparative Example 1 and Comparative Example 2, Shotaro MATAYOSHI, 4 outsiders, "Electrochemical reforming of CH _4- CO ₂ gas-using porous Gd-topped ceramic Electrolyte with Electrolyte with Ni". See of Japan, 2009, 117, 1147-1152. For details of Comparative Example 3, refer to the above-mentioned Non-Patent Document 1.

As mentioned above, based on the findings obtained in Examples 2 to 5, at least the following can be said. _{(1) In the dry reforming of biogas using O 2} gas in the air, the precipitated carbon is oxidized by the supplied air, so that the high durability of the electrochemical reactor is maintained. (2) Cell 2 having metallic Ni on the cathode _{showed a high H 2} generation rate. The catalytic activity of the metal Co of the anode is larger than that of the metal Ru at 600 to 800 ° C.

The above-described embodiments are for explaining the present invention and do not limit the scope of the present invention. That is, the scope of the present invention is indicated not by the embodiment but by the claims. Then, various modifications made within the scope of the claims and the equivalent meaning of the invention are considered to be within the scope of the present invention.

The present invention, fuel gas is particularly suitable for the production of H ₂ -CO mixed fuel.

1 Electrolyte film 2 Cathode 3 Anode 4 Tube 5 Applying part 6 Holding part 7 Supply part 8 Temperature control part 100 Electrochemical reactor 200 Fuel gas manufacturing system

Claims (7)

A cathode containing a first metal selected from the group consisting of nickel, ruthenium and cobalt,
An anode containing a second metal, ruthenium or cobalt,
A porous electrolyte membrane that is interposed between the cathode and the anode and contains a metal oxide that allows oxide ions to permeate.
With
Oxidizing agent gas and biogas containing oxygen are supplied toward the cathode.
Electrochemical reactor. The first metal is
Nickel
The second metal is
Cobalt,
The electrochemical reactor according to claim 1. The oxidant gas is
It ’s air,
The ratio of the number of moles of methane contained in the biogas to the total number of moles of oxygen and carbon dioxide contained in the biogas and the air, respectively, is
1: 0.9 to 1.1,
The electrochemical reactor according to claim 1 or 2. The electrochemical reactor according to any one of claims 1 to 3 and
A supply unit that supplies the oxidant gas and the biogas toward the cathode, and
A fuel gas manufacturing system. An application unit for applying a pulse voltage between the cathode and the anode is further provided.
The fuel gas manufacturing system according to claim 4. Further provided with a holding portion for holding the oxidant gas and the biogas,
The supply unit
The oxidizing agent gas and the biogas held in the holding portion are supplied toward the cathode.
The fuel gas production system according to claim 4 or 5. An intervening cathode containing a first metal selected from the group consisting of nickel, ruthenium and cobalt, an anode containing a second metal such as ruthenium or cobalt, and oxidation between the cathode and the anode. A method for producing a fuel gas using an electrochemical reactor including a porous electrolyte membrane containing a metal oxide that allows material ions to permeate.
An application step of applying a voltage between the cathode and the anode,
A supply step of supplying oxygen-containing oxidant gas and biogas toward the cathode, and
A method for producing fuel gas, including.

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